Research in twins defines shared features of the human gut microbial communities: variations linked to obesityDecember 03, 2008Trillions of microbes make their home in the gut, where they help to break down and extract energy and nutrients from the food we eat. Yet, scientists have understood little about how this distinctive mix of microbes varies from one individual to the next. Now, by cataloging the microbial species in the guts of lean and obese, identical and fraternal female twins and their mothers using a new generation of powerful DNA sequencers, researchers at Washington University School of Medicine in St. Louis have discovered that each individual carries a unique collection of bacteria, although the communities are more similar among family members. When the scientists looked more deeply at the microbes' DNA, they found a striking similarity: The various collections of bacterial species carried a common set of genes that performed key functions to complement those performed by our human genes. The study is available in the advance online Nature. "Although there are differences in who's there among our individual gut communities, these different assemblages of microbes carry a common core set of genes that perform key functions. These functions supplement those carried out by our human genes," says senior author Jeffrey I. Gordon, M.D., director of Washington University's Center for Genome Sciences. Furthermore, when the study's lead author Peter Turnbaugh, a graduate student working in Gordon's lab, sequenced the microbial community DNA, or microbiome, of a subset of obese and lean twin pairs, he found that obese individuals had an increased representation of nearly 300 bacterial genes, many of which are devoted to extracting calories from food and processing nutrients. This new evidence supports Gordon's earlier research in mice that established a link between obesity and the efficiency of energy harvest from the diet by gut bacteria. To compare gut bacterial communities both within and between families, Gordon and his colleagues obtained stool samples from 31 identical twin pairs, 23 fraternal twin pairs and 46 of their mothers. The twins were in their 20s and 30s and of European or African ancestry. Each twin pair was generally either lean or obese as defined by the Body Mass Index (BMI). All twins were born in Missouri, but they now live throughout the country. They are participants in the Missouri Adolescent Female Twins Study, a long-standing study of Missouri-born twins led by Washington University's Andrew Heath, Ph.D., professor of psychiatry, which is designed to decipher the influence of environment versus genetics on aspects of human health. In the current study, each individual provided stool samples two months apart, enabling the researchers to track fluctuations in bacterial communities over time. The women had not taken antibiotics, which are known to alter the gut community, for at least six months. Initially, the researchers sequenced a gene found in all microbes. This gene, 16S rDNA, functions as a barcode of life and can be used to catalog the species present in a microbial community without having to culture the bacteria. Surprisingly, they did not find a single abundant bacterial species shared in the intestines of the study's 154 participants. While family members were more likely to harbor similar collections of bacterial species, the degree of similarity was the same for identical as for fraternal twin pairs, regardless of whether they lived in the same house or in different regions of the United States, the researchers found. "This suggests that early environmental exposures play a key role in determining which microbes colonize our intestinal tracts," Gordon says. "It appears that we acquire an enormous number of genes - in the form of our microbial genes - from our early environment." These microbial genes, together with our human genes, form our 'metagenome." The current research is part of the ongoing human microbiome project, which seeks to not only catalog the microbial species and genes associated with healthy bodies and certain disease states, but to understand how our microbial communities function. Microbial cells are estimated to outnumber human cells by a factor of ten to one. Collectively, the microbes are estimated to carry far more than the 20,000 genes that make up the DNA that we inherit from our parents. "This study opens many doors to areas that are important to explore," Gordon says. "But before we can confidently associate changes in our indigenous microbial communities with risk for certain diseases, it is very important that we define the normal variations that occur in these communities within and between individuals, and the factors that might drive these variations in our microbial ecology. We are interested in understanding how our modern lifestyles, changing cultural traditions, new technologies, and Western diets are shaping our gut microbiome. We should consider another dimension of human evolution, namely that which is occurring at the level of our microbiomes, as our societies undergo rapid transformation. We think that studying twins living in different parts of the world represents a particularly useful way to move this new area of research forward." The research was supported by the National Institutes of Health, the National Science Foundation, the W.M. Keck Foundation and the Crohn's and Colitis Foundation of America. Turnbaugh PJ, Hamady M, Yatsunenko T, Cantarel BL, Duncan A, Ley RE, Sogin ML, Jones WJ, Roe BA, Affourtit JP, Egholm M, Henrissat B, Heath AC, Knight R and Gordon JI. A core gut microbiome in obese and lean twins. Online Nature. Washington University School of Medicine in St. Louis |
|||||||||||||||||||||
| Related Microbes Current Events and Microbes News Articles Cigarettes Harbor Many Bacteria Harmful to Human Health Cigarettes are "widely contaminated" with bacteria, including some known to cause disease in people, concludes a new international study conducted by a University of Maryland environmental health researcher and microbial ecologists at the Ecole Centrale de Lyon in France. Tiny bubbles clean oil from water Small amounts of oil leave a fluorescent sheen on polluted water. Oil sheen is hard to remove, even when the water is aerated with ozone or filtered through sand. MIT scientists pinpoint origin of dissolved arsenic in Bangladesh drinking water Researchers in MIT's Department of Civil and Environmental Engineering believe they have pinpointed a pathway by which arsenic may be contaminating the drinking water in Bangladesh, a phenomenon that has puzzled scientists, world health agencies and the Bangladeshi government for nearly 30 years. Earth's early ocean cooled more than a billion years earlier than thought: Stanford study The scalding-hot sea that supposedly covered the early Earth may in fact never have existed, according to a new study by Stanford University researchers who analyzed isotope ratios in 3.4 billion-year-old ocean floor rocks. Early life on Earth may have developed more quickly than thought The Earth's climate was far cooler - perhaps more than 50 degrees - billions of years ago, which could mean conditions for life all over the planet were more conducive than previously believed, according to a research team that includes a Texas A&M University expert who specializes in geobiology. Sweet as can be: how E. coli gets ahead Scientists at the University of York have discovered how certain bacteria such as Escherichia coli have evolved to capture rare sugars from their environment giving them an evolutionary advantage in naturally competitive environments like the human gut. Newly Discovered Fat Molecule: An Undersea Killer with an Upside A chemical culprit responsible for the rapid, mysterious death of phytoplankton in the North Atlantic Ocean has been found by collaborating scientists at Rutgers University and the Woods Hole Oceanographic Institution (WHOI). This same chemical may hold unexpected promise in cancer research. New imagining technique could lead to better antibiotics and cancer drugs A recently devised method of imaging the chemical communication and warfare between microorganisms could lead to new antibiotics, antifungal, antiviral and anti-cancer drugs, said a Texas AgriLife Research scientist. Nitrogen loss threatens desert plant life, study shows As the climate gets warmer, arid soils lose nitrogen as gas, reports a new Cornell study. That could lead to deserts with even less plant life than they sustain today, say the researchers. Scientists visualize how bacteria talk to one another Using imaging mass spectrometry, researchers at the University of California, San Diego have developed tools that will enable scientists to visualize how different cell populations of cells communicate. More Microbes Current Events and Microbes News Articles |
|||||||||||||||||||||
|
|||||||||||||||||||||
|
|||||||||||||||||||||